1. Field of the Invention
The present invention relates to a horizontal conveying apparatus such as a flow-through rack used for conveying a pallet in a horizontal direction from an entrance port thereof to an exit port thereof, with either a load or an article mounted on the pallet, and particularly, to an improvement in that the pallet is mounted on a rail laid in the horizontal direction and is conveyed intermittently along the rail.
2. Description of the Related Art
As is well known, in various stockrooms of production factories, flow-through racks are widely used. The flow-through rack is arranged so as to automatically and sequentially convey loads through an entrance port, provided at one end portion of the flow-through rack, to an exit port provided at another end portion of the flow-through rack, by means of a horizontal conveying apparatus. Therefore, it is possible to sequentially convey the loads out of the exit port, in the order in which the loads are conveyed from the entrance port.
A horizontal conveying apparatus generally used for this kind of flow-through rack is arranged such that a number of rollers are rotatably supported by a rail provided so as to move a load downwardly at an inclination from an entrance port to an exit port. Further, since loads are mounted on the rollers at the entrance port, the loads self-advance to the exit port, due to gravity, the inclination of the rail, and the rotation of the rollers.
However, in this general kind of horizontal conveyer, since the rail must be inclined to provide a gap between the entrance port and the exit port, there occurs a problem in that a dead space is created. This dead space is unnecessary for storing the loads. In addition, there occurs a problem in that it is not possible to avoid a variation in the moving speed, depending on the degree of the roughness of the bottom surfaces of the loads.
For example, a horizontal conveying apparatus which solves this kind of problem is disclosed in Japanese Patent Application (KOKAI) Publication No. 2-300,012. In the horizontal conveying apparatus shown in this example, at first, a lengthwise conveying member is horizontally extended from the entrance port of the loads to the exit port. This conveying member is supported so as to be reciprocally movable by a constant stroke in the lengthwise direction, with a load mounted thereon.
In addition, a lengthwise support member is provided in parallel with the conveying member. A plurality of stopper pieces are provided at constant intervals along the lengthwise direction. Each of these stopper pieces normally keeps a standing attitude such that these stopper pieces project upwardly, and each is arranged such that each of the stopper pieces falls down as the front side of the load pushes each stopper piece when each load moves from the entrance port to the exit port. Each stopper piece is engaged on the back side of each load when the loads are moved in the reverse direction.
Specifically, loads mounted on the conveying member are allowed to move without being stopped by stopper pieces when these loads are moved from the entrance port to the exit port. The loads are stopped by the stopper pieces and are prevented from moving when the loads are moved from the exit port to the entrance port. Therefore, the conveying member repeats reciprocal movements, thereby intermittently conveying the loads from the entrance port to the exit port.
According to the horizontal conveying apparatus shown in this prior art example, the conveying member can be placed horizontally without being inclined, so that it is possible to prevent occurrence of a dead space which is not directly necessary for storing the loads, like in a conventional apparatus. In addition, since loads are moved with themselves mounted on the conveying member, the moving speed can be kept constant regardless of the weights of the loads and the degree of the roughness of the bottom surfaces of the loads.
However, in the conventional horizontal conveying apparatus as described above, at the time when movement of a load mounted on the conveying member from the entrance port to the exit port is completed by one forward movement of the conveying member, there appears a distance between the back surface of the load mounted on the conveying member and the stopper piece which is closest to the back surface and is still standing, in a normal case.
Therefore, when a load is reversibly moved from the exit port to the entrance port due to a backward movement, the load can move back towards the entrance port together with the conveying member until the back surface of the load is brought into contact with and is stopped by a standing stopper piece. Specifically, the distance over which a load is conveyed by a forward movement of the conveying member is shortened, resulting in a problem that the efficiency of the conveying operation is deteriorated.
In addition, a load being moved toward the exit port is prevented from moving in the reverse direction since the back surface of the load is in contact with the stopper piece. Thereafter, the load is moved again toward the exit port, by the next forward movement of the conveying member. These conveying movements are repeated, and then, the loads are conveyed while being swung forwardly and backwardly in the conveying direction, resulting in a problem that the loads are either damaged or disarranged.